The field of this invention is gas injection apparatus; more specifically, a gas injection apparatus for injecting a quench gas into a lined vessel.
When handling gases at elevated temperatures, it is sometimes necessary to inject a quench gas into the stream of hot gases. One of the processes in which injection of a quench gas is necessary is the coal gasification process. In the coal gasification process, a coal slurry is partially oxidized in a refractory lined gasifier vessel, producing a gas and a residue consisting of soot and molten slag. The hot gas discharged from the refractory lined gasifier is cooled in a radiant boiler to the point at which the molten slag is at least partially solidified but still sticky. The quench gas is utilized to cool the sticky residue to a temperature where it can be easily separated from the coal gas. In addition, to aiding in the separation of the fine particulate residues, the quench gas also lowers the temperature of the gas itself. The vessels and ducts used in this process are all lined either with refractory as in the gasifier or with a water wall as in the radiant cooler, because the temperature of the coal gas is in the range of 800.degree. F. to 2500.degree. F. Because of the problems associated with the injection of a quench gas in a lined vessel, producers of coal gas have had difficulty incorporating this step into their process.
One of the purposes of the liner in these vessels is to protect the vessel wall from being subjected to the high temperatures associated with the coal gas. Necessarily then, the liner is subjected to higher temperatures and larger temperature variations than the vessel wall. Because of this, the liners are installed in a manner allowing the inner liner to expand and contract independently of the vessel wall. The allowance of independent thermal expansion and contraction creates problems in providing a means for injecting a quench gas into the hot gaseous stream. To accomplish injection, a duct must pass through the vessel wall, bridge the gap between the vessel wall and the inner liner, and attach to the inner liner. In this arrangement the supply duct is subjected to external thermal stresses created by the independent contraction and expansion of the inner liner with reference to the vessel wall; and, is also subjected to internal thermal stresses as one end of the duct will be at a higher temperature than the other end since the liner is at a higher temperature than the vessel wall.
Other problems arise from the way the quench gas is injected into the hot coal gas. For the injection of the quench gas to be effective the gas must be injected such that there is adequate mixing of the quench gas and the hot coal gas. It has been determined that this mixing can best be achieved by injecting the quench gas normal to the flow of the hot coal gas. Since the vessels handling the hot coal gas are lined the radial injection normally results in the destruction of the integrity of the inner liner. The integrity is destroyed since gaps in the liner are created to allow the gas to be injected into the coal gas. The creation of gaps or elimination of the liner at the point of injection is not an adequate solution as the vessel walls will then be subjected to the hot raw coal gas. Attempts to minimize the gaps and maintain the liner's integrity have resulted in an increase in the number of fittings and headers. Increasing the number of fittings and headers in the liner is not an adequate solution as these extra fittings and headers provide additional points of potential failure for the inner liner.
As a result of these problems coal gas producers have either eliminated the injection of a quench gas from their process, causing operating problems, or adopted an injection method that eliminates the inner liner, resulting in high maintenance.